Design and Fabrication of Sic Micro-Transducers With Large Q-Factors for High Resolution Sensing

Abstract

Gravimetric sensing with microresonators is the most accurate means for molecular recognition applications, i.e. specific molecule sensing. The molecular recognition sensitivity is determined by frequencyquality factor (fQ) figure of merit, which is influenced by resonator’s type, geometry, material, and damping parameters. Cubic silicon carbide has outstanding mechanical and chemical properties, which make it excellent for resonant sensing applications. We have fabricated epitaxial silicon carbide on silicon resonators using silicon surface micromachining. We demonstrate that outstanding fxQ products could be achieved on string resonators: by increasing the length and the tensile stress, by high vacuum operation, and by improvement of crystal quality and clamping condition. We have achieved fxQ products in the order of ~1012 Hz, which are better than the state-of-the-art silicon nitride strings. We also show the reduction of metal damping by growing graphene overlayer on epitaxial silicon carbide membranes, through a novel transfer-free alloy-mediated approach, for electrical transduction purposes. We report that graphene results in much smaller quality factor reduction (factor of 2) as compared to conventional metals overlayer (an order of magnitude). This is the highest transfer-free quality graphene reported so far on large silicon substrates; based on solid source growth from epitaxial silicon carbide.